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Re: [PATCH] ld: add support for LOG2() in linker scripts

On Tue, 23 Jul 2013, Clemens Lang wrote:

> On Mon, Jul 22, 2013 at 06:26:26PM -0400, Hans-Peter Nilsson wrote:
> > But why the floor of the log2; why round towards 0?
> >
> > I'd think rounding against infinity, but with 0 yielding 0,
> > would be more useful, yielding the required power of 2 of the
> > memory size to contain the region.  You wouldn't be interested
> > in 75k yielding "16" (as 64k); for anything above 64k up to 128k
> > you'd want "17"; a 128k memory is needed.  That seems to match
> > your requirement description as well.
> >
> > How about tweaking this to instead yield the ceiling of the log2
> > (with 0 yielding 0)?
> I agree that this is more useful in the context of linker scripts. I
> initially didn't implement it this way, because it seemed uncommon to me
> that a function called "LOG2" returning an integer rounds towards
> infinity.
> What about two variants of the funtion, LOG2FLOOR and LOG2CEIL? Or
> should I just ignore the ambiguity and have LOG2 round up?

FWIW, I don't have any particularly strong opinion either way.
Though I think you'd prefer going for the simplest solution and
just have one function, when adding the missing test-cases. ;)

brgds, H-P

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